Various isotopes are in high demand for carrying out basic research and also for a variety of industries such as those involved in medicine and energy. In order to be useful, the isotopes are often required in sufficiently high concentration, which may be higher than the naturally occurring abundance of the isotopes. In such situations, the isotopes need to be enriched in concentration relative to their naturally occurring state.
Enrichment of desired isotopes of a common element is extremely difficult due to the isotopes having little if any differences in a variety of their chemical and physical properties. Chemical and physical processes are commonly used for separating atoms of different elements. But such processes are generally not suitable for separating the atoms of an element into different isotopes.
One example of a prior approach to isotope separation involves gaseous diffusion, such as the methods described by W. W. Watson, “Concentration of heavy carbon by thermal diffusion,” Physical Review, 56:703 (1939) and W. H. Furry et al., “On the theory of isotope separation by thermal diffusion,” Physical Review, 55:1083-1095 (1939). Another example involves ultra-centrifuge separation such as described by J. W. Beams et al., “The separation of isotopes by centrifuging,” Physical Review, 50:491-492 (1936). Yet another example of an isotope separation system was the Calutron used during World War II.
Lasers have also been used in isotope separation. In general, such methods involve using a laser to illuminate a vapor sample that includes a mix of isotopes of an element. The laser is tuned to a specific wavelength so that only one desired isotope from the variety of isotopes is excited to an ionized state. In such a process, finely tuned lasers interact with only one isotope. After the desired isotope has been ionized, it can be separated from other the isotopes in the sample by applying an electric field. This method has been referred to as AVLIS (atomic vapor laser isotope separation).
Despite significant interest, the progress of isotope separation technology has advanced slowly. What is needed are more effective or more readily adapted processes, as compared with prior technology, for separating isotopes of elements that are found in nature as mixtures of various isotopes. In various situations, it would be helpful to have techniques that can isolate isotopes with a low natural abundance. In other situations, it would be helpful to be able to purify samples of isotopes that have a moderate or high natural abundance.